HCV NS5A is a 447 amino acid phosphoprotein which lacks a defined enzymatic function. It runs as 56 kd and 58 kd bands on gels depending on phosphorylation state (Tanji, et al. J. Virol. 69:3980-3986 (1995)). HCV NS5A resides in replication complex and may be responsible for the switch from replication of RNA to production of infectious virus (Huang, Y, et al., Virology 364:1-9 (2007)).
Multicyclic HCV NS5A inhibitors have been reported. See U.S. Patent Publication Nos. US20080311075, 0520080044379, US20080050336, US20080044380, US20090202483 and US2009020478. HCV NS5A inhibitors having fused tricyclic moieties are disclosed in International Patent Publication Nos. WO 10/065681, WO 10/065668, and WO 10/065674.
Other HCV NS5A inhibitors and their use for reducing viral load in HCV infected humans have been described in U.S. Patent Publication No. US20060276511.
The compound dimethyl((2S,2′S)-((2S,2′S)-2,2′-(5,5′-(6-phenyl-6H benzo[5,6][1,3]oxazino[3,4-a]indole-3,10-diyl)bis(1H-imidazole-5,2-diyl))bis(pyrrolidine-2,1-diyl)bis(3-methyl-1-oxobutane-2,1-diyl))dicarbamate (hereinafter designated as “Compound A”) is a potent HCV NS5A inhibitor. The structure of Compound A is as follows:

Compound A is disclosed in US Patent Publication No. US20120083483.